Retrofit: REST API call करें

<!-- AndroidManifest.xml -->
<uses-permission android:name="android.permission.INTERNET" />

# libs.versions.toml
retrofit = "2.11.0"
retrofit = { group = "com.squareup.retrofit2", name = "retrofit", version.ref = "retrofit" }
retrofit-converter-gson = { group = "com.squareup.retrofit2", name = "converter-gson", version.ref = "retrofit" }

// app/build.gradle.kts
implementation(libs.retrofit)
implementation(libs.retrofit.converter.gson)

package com.codingeasily.studentdiary.network

/** Matches one object in https://codingeasily.in/api/android-tips.json */
data class Tip(
    val id: Int,
    val title: String,
    val text: String,
    val image: String,
    val link: String
)

data class TipsResponse(val tips: List<Tip>)

package com.codingeasily.studentdiary.network

import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory
import retrofit2.http.GET

/** Retrofit turns this interface into real HTTP code. */
interface TipsApi {
    @GET("api/android-tips.json")
    suspend fun getTips(): TipsResponse

    companion object {
        private const val BASE_URL = "https://codingeasily.in/"

        val service: TipsApi by lazy {
            Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build()
                .create(TipsApi::class.java)
        }
    }
}

// From Student Diary – NoteViewModel
private val _tip = MutableLiveData<TipState>()
val tip: LiveData<TipState> = _tip

fun loadTip(force: Boolean = false) {
    if (!force && _tip.value is TipState.Success) return
    _tip.value = TipState.Loading
    viewModelScope.launch {
        _tip.value = try {
            val tips = TipsApi.service.getTips().tips
            if (tips.isEmpty()) TipState.Error("No tips yet")
            else TipState.Success(tips[(System.currentTimeMillis() / 86_400_000L % tips.size).toInt()])
        } catch (e: Exception) {
            TipState.Error(e.message ?: "Network error")
        }
    }
}

interface ShopApi {
    // GET products.php?category=3&page=1
    @GET("products.php")
    suspend fun products(@Query("category") categoryId: Int, @Query("page") page: Int = 1): ProductListResponse

    // GET product/15
    @GET("product/{id}")
    suspend fun product(@Path("id") id: Int): ProductResponse

    // POST JSON body {"email": "...", "password": "..."}
    @POST("auth/login.php")
    suspend fun login(@Body body: LoginRequest): LoginResponse

    // POST form fields (application/x-www-form-urlencoded)
    @FormUrlEncoded
    @POST("feedback.php")
    suspend fun feedback(@Field("name") name: String, @Field("message") message: String): SimpleResponse

    // header for logged-in calls
    @GET("orders.php")
    suspend fun orders(@Header("Authorization") bearer: String): OrdersResponse

    // when you need the status code
    @GET("profile.php")
    suspend fun profile(): Response<ProfileResponse>
}

try {
    val res = api.profile()                      // Response<ProfileResponse>
    if (res.isSuccessful) show(res.body()!!)
    else if (res.code() == 401) logout()
    else showError("Server error ${res.code()}")
} catch (e: IOException) {                       // no internet, timeout
    showError("Check your internet connection")
} catch (e: HttpException) {                     // non-2xx when return type is not Response<>
    showError("HTTP ${e.code()}")
}

// timeouts + logging (add com.squareup.okhttp3:logging-interceptor)
val client = OkHttpClient.Builder()
    .connectTimeout(15, TimeUnit.SECONDS)
    .readTimeout(20, TimeUnit.SECONDS)
    .addInterceptor(HttpLoggingInterceptor().apply { level = HttpLoggingInterceptor.Level.BODY })
    .build()
Retrofit.Builder().baseUrl(BASE_URL).client(client).addConverterFactory(GsonConverterFactory.create()).build()